1. Field of the Invention
The present invention relates generally to a well head containment fitting device for attachment to a production wellhead that has ruptured or otherwise presents an uncontrolled leak, and more particularly, to such a device as used to cap a deep water petroleum well that has become uncontrollable from failure of its safety systems.
2. Background Art
A typical production wellhead in an underwater setting includes a rod string extending from the water surface to a wellbore beneath the surface containing a fluid, such as hydrocarbons, and a driving or pumping unit connected to the rod string for producing the fluid from the wellbore. When the underwater oil well is under water, especially in very deep water, that is, over 3000 feet (1000 meters), and in certain other instances, the hydrocarbon, either in gas or liquid form, is under a great deal of pressure even exceeding 2000 psi (13,780 dyne/sq.m.).
Many of the known containment devices are designed to simply collect the escaping fluid within a container or chamber as the escaping fluid remains in a freely flowing form, that is, the devices contain the flowing liquid being ejected at great pressure in a containment vessel, and evacuate it as it is collected. Although the fluid may be collected in the container, the fluid is not intended to be retained within that container, but must be evacuated to permit the further collection of continuing flow of liquid. Each of the prior art devices includes a drain, drain valve or drain tubing such that the liquid can be withdrawn from the containment vessel. Prior art devices provide for the flow of the fluid out of the device through the drain. The drained fluid is then collected for disposal in a second storage container, typically located apart from the device, and usually on the surface of the water under which the wellhead rests.
Since the leaking fluid necessarily flows freely within these devices, a tight seal between the device and the stuffing box must be maintained during operation of the device in order to prevent leakage and spills from the device into the environment, whether undersea or floating to the surface. Precautions are also required to prevent leakage or spills from either the drain structure or the secondary storage containers into the environment.
To further explain the known methods of spillage containment, the process of the undersea wellhead will be discussed. Typically, the wellhead is drilled after a number of safety devices are in place, so that when the petroleum or other fluid that is being produced by the wellhead begins to flow under great pressure to the surface for collection, sufficient mechanisms and ample redundancy in the system are in place to shut down the wellhead at or near the source in the event that any problems develop.
For example, fluid produced from the wellhead sometimes includes a significant portion of heavy oil, or includes sand, clay or other particulate matter, which causes stress to develop in the equipment due to sluggish flow of the dense or particle containing liquid. In such a case, the pipes and other devices that are used to evacuate the fluids from the wellhead may become clogged or blocked, thus preventing proper drainage from the device. In very deep waters, the extreme pressures and large distances from the warming rays of the sun, otherwise available in waters closer to the surface, cause the water to be reduced to very low temperatures, even below the normal freezing point of water (at the surface). When these devices are used in colder climates, escaped fluid may freeze within critical junctions of the device or within the drainage means, such as pipes, preventing proper flow of fluid therethrough. If the drainage means is incapable of functioning properly, the fluid can collect within the device until the containment vessel is so full as to render it inoperative to further collect fluid. In that case, the fluid finds a weak spot in the device and begins to leak into the environment.
Other problems can develop when there is a significant amount of natural gas entrained in petroleum being produced. When such a fluid mixture reaches the surface, the natural gas goes out of solution and creates pockets within the piping and equipment, and under extreme circumstances may lead to explosive and sometime catastrophic conditions. Such an event occurred at an undersea wellhead in the Gulf of Mexico in 2010, leading to a major environmental disaster.
Leaking fluid is not desirable because not only is there a loss of production because the fluid is no longer being collected, but most importantly, severe damage to the environment occurs if the fluid is permitted to leak externally in large amounts. Thus, the wellhead systems must continue to operate normally, or the system must have a mechanism to ensure shut down of the fluids being pumped out of the wellhead. Thus, to ensure shut down and to reduce delay in the shut down, a large number of redundant systems are necessary to ensure that the flow of fluid ceases when needed. On occasion, and as has been widely reported in press reports, the wellhead may develop these and other problems that, if left unchecked, cause the wellhead to completely malfunction, requiring the wellhead to be shut down and production to cease.
A major environmental disaster can occur when the wellhead loses all the redundancy and cannot be shut down when a fluid leak develops. For example, once a rupture in the pipe system that is draining the wellhead production is complete, the safety systems are brought to effect to shut down the flow completely, thereby to permit repairs to be made. If one or more of the safety systems are inoperative for whatever reason, then the redundant systems are brought into operation to complete repairs so that the functional systems are all operating normally. If all the redundancy fails, then the a serious problem develops and the wellhead becomes a runaway leak spewing fluid directly from the wellhead opening and any broken piping that is in place, causing a spill that requires remediation action, such as collecting as much as possible of the spilled fluid at the surface. This is not always feasible in deep open water, especially in unfavorable weather conditions. Because of the serious environmental damage results from a runaway well, it becomes imperative to cap the well and stanch the fluid flow so that the well can be repaired or permanently capped.
A need exists in the industry for a device for shutting of the fluid flow and collecting and retaining the fluid which tends to escape from the wellhead between the top of the stuffing box and the rod string in the event of failure of all the redundant safety systems. The procedure must be able to operate in the high pressure and cold water environment of deep water drilling. Further, there is a need for the device to remove the fluid from the well as it is being shut down, and to remove the fluid in an efficient and efficacious manner, as compared to prior art devices, so as to inhibit leakage and which minimizes the risk of leaks or spills to the environment.